WELL . . .
I purchased the above referenced firearm online from a respected dealer. All the descriptions I have given about this weapon came from a phone conversation. Well, the gun arrived at my local FFL dealer today. I went to pick it up, and it is a BEAUT, even better than the picture indicates: clean, tight action, etc.
At the end of my inspection, I checked the serial # on the butt. It was NOT the one the dealer told me over the phone. He told me "C 484xx", but this one read "551xxx".

HUH??
Turns out the online dealer had TWO earlier M&Ps in his store. The piece I received was in fact the one pictured, but his assistant had read me the wrong specs over the phone. Mine was not made in the 1950s, but instead is an M&P of 1905, 4th change, circa 1922-24!
WOW! It's not exactly $15 Aldens, but . . . "me so happy"!
RaiderZee